The curtains in Wang Yu’s home blocked the light well. Though it was still daytime, the room plunged into darkness the moment they were drawn.

Yan Qing wheeled herself to a position beneath the window. Finding a suitable spot, she leaned forward and gently sprayed the contents of the small bottle onto the floor.

The entire room held its breath. No one dared to make a sound.

Yan Qing had taken nothing more than a partial body and guided the Military Police Directorate to “Wang Yu.” The admiration she had earned among its ranks now bore no resemblance to the skepticism of her first days.

No one doubted her now. Everyone waited in quiet anticipation for a miracle.

And the miracle unfolded before their eyes, just as they had hoped.

Where Yan Qing had sprayed the bottle, the floor began to glow — a ring of blue-green luminescence, brilliant and striking, like fireflies dancing in a night sky, mysterious and elusive.

As the onlookers were still catching their breath in wonder, the faint glow gradually dimmed and faded, until it vanished entirely.

Bai Jin cried out in astonishment, “What is that?”

“Blood.”

“Blood can glow?”

“It’s not that blood glows — it’s that this substance makes it glow. It’s called luminol — a chemical reagent.” Yan Qing sprayed another section of the floor. “Surely Dr. E has come across the name before?”

E’Yuan had indeed seen it mentioned in a book during his time abroad, though at the time no one had known what practical use it might have.

“When luminol is oxidized, it emits a blue light. Human blood contains hemoglobin, and hemoglobin contains iron…” Yan Qing noticed that the men around her were all staring at her with wide eyes — clearly with no knowledge of chemical elements whatsoever. If she went any further into the science, she feared she would lose them completely.

She settled for a concise explanation instead. “Simply put, luminol can reveal traces of blood in quantities as small as one part per million. The criminal repainted the walls, but he could not repaint the floor — only scrub it. As long as luminol is present, even if he washed this room ten times over, traces would still be detected.”

“Remarkable!” Bai Jin clapped his hands in amazement.

E’Yuan approached with curious eyes. “Miss Yan, may I try?”

The E’Yuan who had once barely deigned to lift an eyelid in Yan Qing’s direction — a man who had seemed to have arrogance written into every cell of his body — now spoke with unmistakable respect.

Yan Qing handed him the spray bottle without dwelling on his earlier conduct.

The results proved luminol’s power beyond all doubt. Under E’Yuan’s hands, the floor of the room revealed vast swaths of blood traces. It was now certain: if Wang Yu was Huo Li’s killer, then this was the primary crime scene, and forensic evidence could be collected here.

E’Yuan continued with luminol’s assistance, uncovering a pair of shoes with blood-stained soles, as well as a kitchen cleaver and a boning knife in the kitchen — both consistent, to a striking degree, with the instruments Yan Qing had deduced from the body.

Bai Jin pointed to a plate of leftover food in the kitchen cabinet and clicked his tongue with a shake of his head. “This Wang Yu is truly something else — cooking and eating with knives he used to dismember a body. How does he manage to get it down?”

E’Yuan took his new discovery — the luminol — and continued searching toward the riverbank, with several officers draped in bedsheets and quilts serving as makeshift sun shields.

After a thorough search, E’Yuan found a large area of blood traces at the river’s edge. It could be confirmed that the perpetrator had moved the body from the room to the river after killing and dismembering Huo Li, and had thrown the remains into the Liao River from a low bank.

Shi Ting immediately sent officers in life vests out by boat to search the nearby waters for additional remains — for with blood traces alone, Wang Yu would have a thousand excuses to talk his way out. They needed more.

Meanwhile, the two officers standing guard not far from the door spotted a figure approaching along a distant side path with unhurried steps.

—